Can Arctic Char Adapt to Climate Change?

For centuries, in the remote reaches of the north, Arctic char have provided food for Canada's Inuit. In recent decades, other North Americans have come to admire this attractive fish: up-market consumers for its taste, sport fishermen for its spirit and size, often nearly a meter long, and people at large for its appearance. The colours of the Arctic char, depending on its type and the season, can range from greens, browns, and whites to reds and golds like an autumn leaf.

Char could also have a major scientific use: helping to forecast the effects of climate change. The Arctic will be among the hardest-hit areas, and char are the Arctic species par excellence. Circumpolar in distribution, they are the most prevalent and, above 75o North, the only freshwater fish. The char's response to climate change will provide lessons applicable to other species.

Figuring out that forecast is the challenge taken on by Dr. Jim Reist of the Freshwater Institute at Winnipeg, Manitoba, and colleagues in the Department of Fisheries and Oceans (DFO) and the academic world. But it's no simple matter.

"Arctic char would seem ideal for tracking or extrapolating changes," Jim Reist says. "But you need solid baseline data to work from, which tends to be sparse in the north. And for Arctic char, we're still addressing some fundamental biological questions."

Indeed, in the western Arctic, the very identity of Arctic char can be a puzzle. They bear a strong resemblance to Dolly Varden, a closely related species common in steep, tumbling rivers. Mis-identification of the two species can throw off the biological basis of fishery management. In many areas, researchers have had to check every taxonomic detail to clear up confusion.

"Even within the Arctic char species," Jim Reist says, "the variations can be almost bewildering." The diversity starts with their scattered distribution in North America, all the way from lakes in northern Maine and southeastern Quebec to Ellesmere and other islands close to the North Pole.

In mid-latitude areas, many char populations live an anadromous life: raised in rivers and lakes, they migrate in summer to the salt waters of Hudson Bay, the Arctic islands, and the Atlantic, returning to fresh water in the fall. The same rivers and lakes that support sea-run char can also harbour resident char. These are smaller, more subdued in colour, and never leave home.

At top and bottom, sea-run female and male from Kent Peninsula, central Arctic; middle, a resident male. (DFO photo)

The char's cousin, the Dolly Varden, has an even smaller resident type, of muddy, inconspicuous colour. When larger, sea-run fish are spawning, these small resident males can sneak in to fertilize a clutch of eggs without being seen. Thus, within the same species, evolution makes some fish bright and attractive to mates, while others reproduce by stealth.

Over the centuries, Arctic settlements tended to grow up where fish were more plentiful. The name Iqaluit, capital of Nunavut, means "place of fish." From many locations, such as Cambridge Bay on Victoria Island, Inuit move along the coast in summer, to take whales, char, and other foods for subsistence or commerce. But measured against the vast Arctic barrens, human presence is tiny.

For scientists, travel is expensive, while research budgets are limited. So how, in remote areas, can researchers track the life history and July-August migrations of sea-run char? "With difficulty," Jim Reist says. "But one useful method is analyzing otoliths - the earbones of the fish. Work by DFO biologist John Babaluk has shown that as they swim from river to sea, elements such as strontium increase. Thus, the otolith gives us a chemical record, over seasons and years, with indications of where and when the fish have migrated and how they've fared."

Summer spear-fishing and winter gillnetting for Arctic char. ( DFO photos.)

Many Arctic char populations spend their whole life in fresh water. In the high Arctic, permanent ice pens them in. In the south, impassable waterfalls or other obstacles can confine them. Within these closed systems, especially in large and complex lakes, more variations appear. The char develop different sizes, shapes, colours, and feeding relationships. A few grow very large through cannibalism on younger char.

"Arctic char in the Canadian north have a shorter history than many species elsewhere," Jim Reist says. "In some areas, it's less than 10,000 years since the glaciers receded and char could survive. The biodiversity we're seeing is early evolution still at work, with speciation developing."

Now, climate perturbation is bringing new challenges, even before researchers have fully figured out the species' past and present circumstances. "Char are changing in unknown ways from an unknown starting point, due to climate change," Jim Reist says.

Still, he and colleagues, including Brian Dempson from DFO Newfoundland, Michael Power from the University of Waterloo, and others including graduate students, are finding ways to forecast the char's fate. In Labrador, a multi-year program has documented the impacts of temperature, snowpack, water levels, and other factors. And the char's present-day behaviour at varying latitudes can foreshadow its responses to climatic change.

Even so, the dozens of factors at work make future effects hard to unravel. On the positive side, warmer temperatures should produce more food in many areas. In the far north, as ice cover lessens, more sea access should bring more anadromy. Longer periods at sea and more food should produce bigger fish. In middle latitudes, char between northern Hudson Bay and Ellesmere Island may show more growth.

But for every plus, there's a minus. For example, higher productivity in many lakes will encourage more char to become resident, with fewer going to sea for their summertime food. Resident fish are smaller, more prone to parasites, and less desirable in fisheries. Warming will also produce more sediment in lakes, lessening egg survival.

Around Baffin Island, char may lose ground to Atlantic salmon and brook trout. Along the Labrador coast, as higher temperatures raise marine productivity, char could get bigger. But for more southern latitudes, including Newfoundland, the Maritimes, southeastern Quebec, and northern Maine, the warming of lakes will shrink the distribution of this cold-water species. Many populations will vanish.

For Arctic char overall, climate change in this century will likely bring more negatives than positives. Both populations and biodiversity will decline. This is bad news for the char, for other Arctic species, and for the Inuit.

How to reduce the damage? This is a challenge for fishery managers, made worse by the frequent scarcity of catch statistics and other basic data. Continuing with present practices may present higher risks of depletion or extirpation. Managing more conservatively, with lower levels of harvest, can cause controversies.

Overall, Jim Reist says, "we've got to take a precautionary approach." Meanwhile, through scientific detective work, he and colleagues are creating a clearer picture of the Arctic char's destiny.